The field of invention is low profile push button switches for use with printed circuit boards and the like, more particularly a spring for use with such circuit board mounted push-button switches.
Printed circuit board (PCB) mounted "push button" switches are an inexpensive means of providing an operator interface on industrial control products. These switches are quite small, and have operators that are not designed to be pressed by human fingers. For this reason, an intermediate interface is used that provides a large target area and a spring biasing the interface outward. Preferably the spring must withstand in excess of one million operations to ensure proper operation for the useful life of the switches.
A known design for an intermediate interface provides a key cap retained in a housing disposed above an operator. A spring in the housing interposed between the operator and the key cap biases the key cap away from the operator. Each adjacent switch has an independent housing, key, and switch assembly, thus preventing the actuation of one switch from affecting the other switches. This solution has multiple parts that are expensive and difficult to assemble when multiple switches are adjacent to each other.
Another known solution, shown in FIG. 9, is to integrally form multiple plastic springs on a faceplate of a single housing. An overlay with printed key caps is adhesively mounted on the face plate identifying the location of each spring and operator disposed below. A key cap is depressed to actuate an operator disposed below the spring. One particular prior art solution has a housing face plate with a plurality of circular apertures. A spring disposed in each aperture has a central portion and a pair of semicircular extensions. The extensions are integrally formed part of the central portion and the face plate. This circular spring design can produce stress levels when a operator is actuated that reduces the spring useful life. Additionally, depressing a spring may cause the adjacent face plate material to deflect actuating adjacent operators.